Problem Background

When building AI agents that interact with external systems, you need a way for the model to invoke specific functions rather than generating plain text responses. Tool calling (also called function calling) solves this by letting you define a schema of functions the model can decide to call during conversation. HolySheep's API endpoint provides OpenAI-compatible tool calling support, which means you can use the same patterns you'd use with the official OpenAI API but route traffic through HolySheep for potentially lower costs and better regional availability.

The typical challenge developers face is migrating existing tool calling code from api.openai.com to a custom base URL like https://api.holysheep.ai while ensuring function definitions, response parsing, and streaming all work correctly. This guide walks through the complete implementation with working code samples and debugging steps.

Applicable Scenarios

Tool calling is the right choice when your agent needs to perform actions beyond text generation. Common use cases include:

- **Database queries**: Agent queries a SQL database based on natural language input - **API integrations**: Agent calls external REST APIs (weather, calendar, CRM systems) - **File operations**: Agent reads, writes, or processes files based on user requests - **RAG pipelines**: Agent retrieves relevant documents before generating answers - **Multi-step workflows**: Agent executes a sequence of function calls to complete complex tasks

If you're currently using HolySheep for simple chat completions and need to add stateful action capabilities, tool calling is your next step.

Configuration Steps

Step 1: Update Your Base URL

The critical change when migrating to HolySheep is setting the correct base URL. Replace https://api.openai.com/v1 with https://api.holysheep.ai/v1.

For direct API calls, your endpoint becomes: 

POST https://api.holysheep.ai/v1/chat/completions

For SDK configurations, see the language-specific sections below.

Step 2: Define Your Tool Schemas

Tool definitions follow the OpenAI function calling schema. Each tool needs a name, description (for model guidance), and parameters schema:

```json { "type": "function", "function": { "name": "get_weather", "description": "Get current weather for a specified city", "parameters": { "type": "object", "properties": { "city": { "type": "string", "description": "City name, e.g. 'Tokyo' or 'San Francisco'" }, "unit": { "type": "string", "enum": ["celsius", "fahrenheit"], "default": "celsius"